linux-kernel - Re: [PATCH] mm/memcontrol.c: add memory allocation result check

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Date:	Mon, 30 May 2016 13:22:18 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Wenwei Tao <ww.tao0320@...il.com>
Cc:	Wenwei Tao <wwtao0320@....com>, hannes@...xchg.org,
	vdavydov@...tuozzo.com, cgroups@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/memcontrol.c: add memory allocation result check

On Mon 30-05-16 17:28:40, Wenwei Tao wrote:
> I think explicit BUG_ON may make the debug easier, since it can point
> out the wrong line.

Does it? NULL ptr dereferencec 6 lines below sounds pretty close to me.
I am not nacking this patch I just think it doesn't add much. If others
think it will be useful I will not object.

> 2016-05-30 16:53 GMT+08:00 Michal Hocko <mhocko@...nel.org>:
> > On Mon 30-05-16 16:45:51, Wenwei Tao wrote:
> >> From: Wenwei Tao <ww.tao0320@...il.com>
> >>
> >> The mem_cgroup_tree_per_node allocation might fail,
> >> check that before continue the memcg init. Since it
> >> is in the init phase, trigger the panic if that failure
> >> happens.
> >
> > We would blow up in the very same function so what is the point of the
> > explicit BUG_ON?
> >
> >> Signed-off-by: Wenwei Tao <ww.tao0320@...il.com>
> >> ---
> >>  mm/memcontrol.c | 1 +
> >>  1 file changed, 1 insertion(+)
> >>
> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> >> index 925b431..6385c62 100644
> >> --- a/mm/memcontrol.c
> >> +++ b/mm/memcontrol.c
> >> @@ -5712,6 +5712,7 @@ static int __init mem_cgroup_init(void)
> >>
> >>               rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL,
> >>                                   node_online(node) ? node : NUMA_NO_NODE);
> >> +             BUG_ON(!rtpn);
> >>
> >>               for (zone = 0; zone < MAX_NR_ZONES; zone++) {
> >>                       struct mem_cgroup_tree_per_zone *rtpz;
> >> --
> >> 1.8.3.1
> >>
> >>
> >> --
> >> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> >> the body to majordomo@...ck.org.  For more info on Linux MM,
> >> see: http://www.linux-mm.org/ .
> >> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
> >
> > --
> > Michal Hocko
> > SUSE Labs
> 
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
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> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>

-- 
Michal Hocko
SUSE Labs